The present invention relates to an electrophotographic photosensitive body capable of suppressing or preventing the generation of vibration noise during the use, an electrophotographic process cartridge using the same, and an electrophotographic apparatus.
An electrophotographic photosensitive drum used for an electrophotographic apparatus or the like is generally manufactured by applying a photosensitive layer etc. on the surface of a metallic, hollow cylindrical base formed of aluminum and the like. Such an electrophotographic photosensitive drum, which is used for an electrophotographic copying machine or a laser printer, sometimes produces various kinds of vibration noise according to operating conditions. For example, it is mentioned in Japanese Patent Laid-Open No. 2-118684 and Japanese Patent Registration Publication No. 2913689 that creaking noise is generated due to the contact of the electrophotographic photosensitive drum with a cleaning blade.
In order to prevent the generation of such noise, some filler element is inserted and fixed to the inside of the hollow cylindrical base of the electrophotographic photosensitive drum. The possible shapes of the filler element include a structure combined with a panel (see Japanese Utility Model Laid-Open No. 62-127567 and Japanese Patent Laid-Open No. 11-305598), a spiral shape (see Japanese Patent Laid-Open No. 8-62878), columnar shape (see Japanese Patent Laid-Open No. 2000-89612), and the like.
The possible materials for the filler element include a porous elastic member (see Japanese Patent Laid-Open No. 63-60481), a lapped member having specific JIS hardness (see Japanese Patent Laid-Open No. 5-35166), polyurethane foam (see Japanese Patent Laid-Open No. 63-271388), a viscoelastic material (see Japanese Patent No. 2913689), a filler element whose coefficient of linear expansion is specified (see Japanese Patent No. 3259554), and so on.
All of the above-described filler elements have an anti-vibration effect at the early stage of use. However, after repeated use, the member is shifted or displaced by the centrifugal force, vibrations, shock, or the like, so that the anti-vibration effect at the early stage can no longer be achieved.
To overcome this problem, the filler element is often fixed with an adhesive. In some cases, the hollow cylindrical base may be deformed by expansion and contraction depending on the kind of adhesive being used, and therefore an adhesive which prevents this deformation has been proposed (see Japanese Patent No. 3139669). However, the use of an adhesive requires the product to stand still until it is cured at the time of production, which takes much time, thereby decreasing the productivity. Also, the recent design that takes recycling into account entails a problem in that when the electrophotographic sensitive drum is disassembled, it is difficult to remove the bonded filler element.
The present invention has been made to solve the above problems of the prior art, and the object thereof is to provide an electrophotographic photosensitive body which is easily manufactured, has no deformation of a hollow cylindrical base and no decrease in anti-vibration effect when repeatedly used, and is equipped with a filler element which can be removed easily at the time of recycling. The present invention further provides a silent process cartridge using the above-mentioned photosensitive body, and an electrophotographic apparatus.
In the present invention, a filler element formed of a viscoelastic material having specific properties and a specific shape is mounted in a drum-shaped electrophotographic photosensitive body (photosensitive drum). As for the properties, a viscoelastic material with a compressive residual strain of 10% or less is used. The compressive residual strain was measured in accordance with JIS (Japanese Industrial Standards) K6401.
By using a filler element formed of a viscoelastic material with a compressive residual strain of 10% or less, the filler element has a sufficient restoring force when being deformed, so that it can be fixed to position without an adhesive. Also, the filler element is not moved by vibration or shock at the time of repeated use, and an anti-vibration effect can be maintained. If the compressive residual strain exceeds 10%, the filler element is not sufficiently fixed to the electrophotographic photosensitive drum because of weak restoring force, and the anti-vibration effect is decreased by repeated use.
Further, the filler element in accordance with the present invention has a construction using a viscoelastic material with a 25% compressive load of 1 kg/cm2.
By this construction, the filler element is provided with a proper flexibility, so that the workability at the time of mounting the filler in the electrophotographic photosensitive drum and at the time of recycling the same is improved, by which the productivity is enhanced. If the 25% compressive load exceeds 1 kg/cm2, the filler element becomes less deformable, so that the workability is degraded. The 25% compressive load was measured at a compression rate of 1 mm/min using a sample with a diameter of 50 mm in accordance with JIS K6301.
Preferably, the filler element has a plate-like body with a thickness of d mm, a length of a mm, and a width of b mm, and the shape satisfies the following expressions (1) to (4):
xcexa3axe2x89xa6Lxe2x80x83xe2x80x83(1) 
xcfx80r/2xe2x89xa6bxe2x80x83xe2x80x83(2) 
d greater than 4xe2x80x83xe2x80x83(3) 
rxe2x88x922d greater than 10xe2x80x83xe2x80x83(4) 
where,
xcexa3a: sum of lengths of inserted viscoelastic material;
L: length of hollow cylindrical base;
r: inside diameter of hollow cylindrical base.
By satisfying expression (1), the filler element in accordance with the present invention can be inserted without protruding from the hollow cylindrical base.
By satisfying expression (2), the filler element can be inserted easily, and after the insertion, the filler element is fixed and will not move.
By satisfying expression (3), the filler element is fixed without moving even if it is subjected to vibration or shock.
By satisfying expression (4), the workability for installing the filler element on an insertion device can be improved.
Since the filler element is fixed to the base by only the force generated by the restoration of the viscoelastic material without the use of an adhesive, at the time of recycling of the electrophotographic photosensitive drum, the filler element can be separated easily from the drum because there are no adhering residues. Also, since the filler elements in accordance with the present invention are inserted and fixed at positions symmetrical with respect to the center in the lengthwise direction of the cylinder, the stability during rotational drive is increased, and swaying due to irregular movement is restrained. Further, a foam is preferably used as the viscoelastic material, and in particular, the use of an urethane foam eliminates the frictional force with the back surface of the base and thus eliminates deterioration due to heat or temperature and humidity at the time of use.
In a process cartridge having a construction in which a cleaning blade is brought into contact with the photosensitive body or an electrophotographic apparatus in accordance with the present invention, the drum-shaped photosensitive body has an especially good anti-vibration effect to prevent vibrations generated when the cleaning blade comes into contact with and slides on the surface of the photosensitive body, so that a very quiet process cartridge or electrophotographic apparatus can be provided.